Compensating system for presses

ABSTRACT

Apparatus for compensating for eccentric loads in forging presses and the like. The apparatus includes a plurality of hydraulic cylinders positioned about the press and connected between the platens. The cylinders are interconnected through a hydraulic integrating device so that if there are eccentric forces acting on the platens the forces within the hydraulic cylinders are automatically shifted to counteract the eccentric forces.

finite States atent Ms Qt t, [451 J. 18, 1972 [54] COMPENSATING SYSTEM FOR 2,976,798 3/1961 Christianson ..100/258 R PRESSES 3,418,923 12/1968 Zeitlin ..72/455 [72] Inventors: Alolu J. Moos, Queens; Alexander Zeltlln, FOREIGN PATENTS OR APPLICATIONS Weschester, both of N .Y.

189,928 5/1957 Austria ..100/258 A [73] Assignee: Barogenlcs, Inc., Pelham Manor, NY.

22 Filed: Oct. 20 9 9 Primary Examiner-Charles W. Lanham Assistant Examiner-Gene P. Crosby PP 867308 Attorney-Meyer,Tilberry and Body 52 us. Cl ..72/453, 100/258 [571 ABSTRACT [51] Int. Cl.. 1B2lj 9/20 A s pparatus for compensating for eccentric loads in forging [58] Field of Search ..100/258 R, 258 A, 46, 72/441, presses and the mm The apparatus includes a plurality of 72/453 hydraulic cylinders positioned about the press and connected between the platens. The cylinders are interconnected [56] References Cited through a hydraulic integrating device so that if there are ec- UNITED STATES PATENTS centric forces acting on the platens the forces within the hydraulic cylinders are automatically shifted to counteract the 2,302,132 11/1942 MacMillin ..100/258 R eccentric f 2,809,542 10/1957 Albers ..100/258 R 2,809,543 10/1957 Zeitlin ..100/258 R 2 Claims, 4 Drawing Figures PATENTEDJAM m SHEET 1 [IF 2 INVENTORS ALOIS -MOOS ALEXANDER ZEITLIN ATTORNEYS.

The present invention is directed toward the press art and, more particularly, to a balance system for compensating for eccentric loads in presses.

The invention is especially suited for use in forging presses of the type having a moving platen and a fixed platen and will be described with particular reference thereto; however, it should be appreciated that the invention is capable of broader application and could be used in many types of presses.

In forging presses wherein cooperating dies act on a workpiece to form it to a desired shape, eccentric loading is frequently encountered. This produces eccentric forces which tend to twist or tilt the platens. Should these eccentric forces become severe enough, the press frame can be seriously damaged. For example, the tie rods can be subjected to unduly high bending stresses.

U.S. Pat. Nos. 2,809,542, and 2,809,543, issued Oct. 15, 1967, to H. B. Albers and A. Zeitlin, respectively, show hydraulic pressure systems which function to compensate for eccentric loads. These prior systems use a plurality of hydraulic pistons and cylinders which are positioned about the movable platen. The movable platen acts against the pistons during the forming portion of the stroke. Any eccentric loading of the platen generates increased pressure in certain ones of the cylinders. The cylinders are connected to act against an accumulator pressure and the arrangement is such that the forces within the various cylinders act to balance the eccentricity.

The problem with systems of the type described in the two above-mentioned patents is that in operation they generate forces which act against the main forging force of the press. Consequently, the available forging force is reduced.

The present invention provides a system which is completely internally balanced. The effect of the system is only to shift the eccentric load to a central position without counteracting the forging force. The invention accomplishes this with a minimum of structure.

In accordance with the present invention, a press of the type including a moving platen and a fixed platen which cooperate to form material therebetween is provided with improved means for counterbalancing eccentric reaction loads on the platens. The means include an even number of double-acting hydraulic cylinder means positioned about the platens with hydraulic circuit means interconnecting diagonally opposite one of the cylinder means so that an increase pressure in any one of the chambers of any one of the hydraulic cylinder means produces a corresponding increase in the opposite chamber of the diagonally opposite hydraulic cylinder means.

The primary object of the invention is the provision of a compensating system of the type described which is internally balanced.

Another object is the provision of a system for balancing eccentric loads in presses which is completely self-contained and which does not require complex controls or force sensing elements.

A further object is the provision of a compensating or balancing system which is easy to construct and which operates without special controls and associated structures.

An additional object is the provision of a compensating system of the type described wherein the compensating effect is doubled without reduction of the main forging force.

Yet another object is the provision of a system of the type described which is simple and highly reliable in operation.

These and other objects and advantages will become apparent from the following description when read in conjunction with the accompanying drawings wherein:

FIG. 1 is an elevational view of the upper portion of a press provided with a balancing system formed in accordance with a preferred embodiment of the invention;

FIG. 2 is a diagrammatic plan view of the press of FIG. 1 showing the fluid connections of the balancing system;

FIG. 3 is a diagrammatic cross-sectional view through the press of FIG. 1 showing a modified form of the invention; and,

FIG. 4 is a modified form of one aspect of the invention showing the manner in which the stroke of the balancing system can be adjusted.

Referring more particularly to the drawings, FIG. I shows the top end of a forging press A provided with a pressure balancing and compensating system formed in accordance with the preferred embodiment of the invention.

The details in construction of the press A are not of particular importance to the invention; however, in the embodiment under consideration the press includes a main frame 10 formed, for example, as shown in U.S. Pat. No. 3,418,923, and comprised of a fixed crosshead 12 formed of a plurality of side-by-side plate members and interconnected with a similar lower crosshead (not shown) by a plurality of tie-rod members 14.

Although the invention could be applied to many types of presses, in the embodiment under consideration, the press is of the moving frame type and has a main fixed platen 16 which is firmly mounted from a suitable foundation tolprovide a rigid immovable platen. Connected subjacent the platen 16 and extending downwardly into engagement with the lower crosshead is a large diameter hydraulic cylinder 18. As can be appreciated, when hydraulic fluid under substantial pressure is applied to the cylinder 18, the reaction of the cylinder causes the lower crosshead to be moved down pulling down the tie rods and the upper crosshead 12 to apply a forging force to cooperating dies carried by the platen l6 and the platen 12 respectively, but not shown in FIG. 1.

As previously mentioned, during the application of the forging forces, it sometimes develops that because of varying thicknesses in the workpiece and other factors, the forces applied are not perfectly centered in axial relation to the press. These eccentric loads tend to overload various components of the press. The subject invention provides an improved means for counterbalancing and compensating for these eccentric loads. In the preferred embodiment these means comprise hydraulic cylinder assemblies 20 and 22 which are connected between the moving crosshead 12 and the fixed platen 16. The two hydraulic cylinder assemblies 20,22 are, in turn, connected in a predetermined manner to two hydraulic integrating units 24 and 26.

Referring again to the hydraulic cylinder assemblies 20,22, it will be noted that both of them are shown as of identical construction; however, as will hereafter become apparent these two units could have differing constructions and take a variety of embodiments while still performing within the scope of the invention. In particular, as disclosed, each of the assemblies 20,22 comprise a first hydraulic cylinder 30 fixedly secured to the moving upper crosshead 12 for movement therewith. Positioned within the cylinders and carried on piston rods 32 are pistons 34. As can be appreciated, the pistons 34 are sealingly and slidably received within the bores of the cylinders 30. Additionally, it will be noted that the piston rods 32 extend upwardly and through the upper ends of the end plates of the cylinders 30. Although not shown, the piston rods 32 are sealed by high pressure seals where they pass through the end plates of the cylinder 30. Each of the cylinders 30 include a valved fluid passage or pipe means 36 which connects opposite sides of the valve through a shutoff valve 38. The structure thus far described provides a hydraulic locking cylinder arrangement so that the piston rods 32 can be locked against movement at any point during the stroke of the pistons 34. Note that with the cylinder 30 filled with hydraulic fluid and the valve open the piston is free to reciprocate through the cylinder since the fluid on one side of the cylinder is merely passed through the valve to the other side of the cylinder however if at any point during movement of the piston the valve is closed then the piston is locked against further movement.

Connected at the lower ends of each of the piston rods 32 are second hydraulic cylinder assemblies 40,42 respectively.

Each of the assemblies 40,42 comprise a piston 44 carried by the respective piston rod 32 and arranged for sliding sealed movement in a cylinder 46. The cylinders 46 are rigidly connected to the fixed platen 16 or the foundation of the press A. The lower ends of each piston rod 32 pass through the end plate of the cylinders 46 and are engaged by a compression spring 48 carried on a frame extending downwardly from the lower plate of the associated cylinder 46. Additionally, a circular housing 50 surrounds the compression springs 48.

The two integrating units 24,26 are interconnected with the hydraulic cylinders 40 and 42 in a manner which will compensate for any eccentric loading movement of the press. As will be apparent, the compensating units could take a variety of specific constructions; however, in the embodiment under consideration they are each identically formed and comprise upper and lower crosshead like members 52,54 respectively. Tie rods 55 extend through the opposed crosshead members 52,54 and are connected thereto by large nuts 56 which function to resist the outward loads acting on the crossheads. A movable crosshead 58 is carried between crossheads 52,54 and arranged for sliding movement on the tie rods 55. Formed in the upper crosshead 52 is a pair of hydraulic cylinders 60,62 in which are received pistons 64,66 respectively. The pistons have their lower surface engaged with or connected to the movable crosshead 58. A somewhat larger diameter cylinder 68 is formed in each of the lower crossheads 54. Connected with each of the cylinders 68 is a hydraulic accumulator 70 which maintains a constant and predetermined pressure on the pistons 72 in the cylinders 68.

The cylinders 60,62 of the integrating units 24,26 are, in turn, connected with the cylinders 46 of the hydraulic piston assemblies 20,22. Note that the cylinder chamber 60a of the unit 24 is connected with the upper portion or chamber portion 46a of hydraulic cylinder assembly 22 the chamber 62a of unit 24 is similarly connected to the chamber 46b of assembly 20. The two chambers 60b and 62b of the integrator 26 are respectively connected with chambers 46c and 46d of assemblies 20,22. This arrangement completes the hydraulic unit connections for the unit.

OPERATION Assume that a workpiece has been placed between the dies and that the cylinder 18 has been actuated to move the frame downwardly to apply a forging force to a workpiece between the dies. At this time the valves 38 are opened and the opposite ends of the hydraulic cylinders 30 are in free communication. As the crosshead 12 moves downwardly the cylinders 30 move with it and the piston rods 32 remain stationary as fluid is simply translated from one side of the cylinders 30 to the other.

As soon as the need arises to actuate the compensating system, the valves 38 are closed so that the pistons 34 and their associated piston rods 32 are hydraulically locked in the cylinder. Consequently, the further movement of the piston rods 32 causes movement of the pistons 44 of the assemblies 40,42.

Assume that an unbalanced reaction force exists with the force acting to the right of the centerline of the press. At such time there is an increase in pressure in chamber 46b of unit 40 and simultaneously an increase in pressure of chamber 62a of the integrating unit 24. With an increase in chamber 62a there must, of course, be a simultaneous decrease in the pressure within chamber 60a since both pistons 64,66 are counterbalanced by the pressure within the large chamber 68. With a decrease in pressure in chamber 60:: there is a simultaneous decrease in the pressure within chamber 46a of the assembly 42. Accordingly, there is an opposite and balanced reaction generated by the hydraulic units 22,20 which reaction will tend to counterbalance the eccentric forces applied through the press. As can be seen, the system is self-starting and the forces, since they are exactly counterbalancing do not reduce the pressure available for forging which pressure is generated by the cylinder l8.

Should an unbalance exist in reactive forces on the opposite side of the centerline of the press the same basic changes take place. That is, the pressure within chamber 460 will increase decreasing the pressure within chambers 62a and 46b, and reducing the pressure in chambers 46c and 6012 while increasing the pressure in chamber 62!; and 46d.

FIG. 4 shows a modified form of the assembly shown in FIG. 1, note that rather than having the upper hydraulic cylinders 30 and their hydraulic interlocking device, this unit merely comprises a main rod which can be driven in vertically adjusted position by a screw rod member 82 driven from a controlled motor gear unit 84 through a conventional right angle drive 86. By actuating the motor the position of the rod 80 can be adjusted so that the compensating effect will begin at any desired point in the forging stroke. Note that the piston rod 32 is engaged by the lower end of the rod 80 at a predetermined point in the stroke depending upon the adjustment of screw 82.

FIGS. 2 and 3 show units in which there are four hydraulic cylinder assemblies with one positioned at each corner of the press equal distances from and uniformly about the press centerline. Referring in particular to FIG. 2, it will be seen that there are four hydraulic cylinder assemblies 90, 91, 92, and 93. These cylinder assemblies are, for example, of the same construction and arrangement as the assemblies 20,22. That is, the assembly cylinders have a piston mounted therein which defines the cylinders into upper and lower chambers. These upper and lower chambers are connected to two separate integrating units 94 and 95. The integrating units are constructed generally the same as units 24,26 of FIG. 1. Note however that there are four of the smaller piston cylinder assemblies formed in the upper crosshead members of the units. Each of these cylinder assemblies are positioned uniformly about the major piston which is in turn connected to an accumulator. In the FIG. 2 embodiment, the dotted line showings represent fluid connections from the lower chamber of each of the cylinders -93 whereas the solid line showings represent the fluid connections from the top half of the respective cylinders.

To explain the operation of the FIG. 2 embodiment assume that there is an eccentric load which has an effective center point as shown at position 2. In such an instance there would be an increase in the pressure in the upper chambers of both of the cylinders 90 and 91. This would accordingly cause an increase in the pressure within the integrator cylinders c and 95d and a decrease in the integrator cylinders 94c and 94d. Consequently, there would be an increase in the pressure acting within cylinders 94a and 94b, as well as, the chambers of cylinders 92 and 93. This would be coupled with a decrease in the upper half or upper chamber of each of the cylinders 92,93. Accordingly, the pressures acting on the movable platen would be such as to balance the eccentric forces generated by the forging.

The same type of relationship would exist no matter where the eccentric load would happen to occur. The cylinder arrangement would always produce a directly counteracting force. Additionally, since the forces produced are exactly opposite, the effective force acting against the hydraulic cylinders supplying the forging force would be 0 thereby not effecting the actual total forging pressures.

The FIG. 3 embodiment shows an arrangement whereby a single integrating unit constructed as described in FIG. 2 for units 94 and 95 can be arranged to perform the same functions as the FIG. 2 embodiment. In the FIG. 4 embodiment there are 4 of the double acting cylinder units -104 positioned between the stationary and moving platens and positioned at each comer of the platens equal distances from the center of the press in the manner described with reference to FIG. 2.

The cylinder units 100-!04 are connected with the cylinders of the integrating unit 104 in the following manner:

The upper chamber of cylinder 100 and the lower chamber of cylinder 103 are both connected with integrating cylinder 104b;

The lower chamber of cylinder 100 and the upper chamber of cylinder 103 are both connected with integrating cylinder 1040;

The upper chamber of cylinder 102 and the lower chamber of cylinder 101 are both connected with integrating cylinder 104d; and,

The lower chamber of cylinder 102 and the upper chamber of cylinder 101 are both connected to integrating cylinder 104a.

In operation of the FIG. 4 embodiment, assume, for exampic, that an eccentric load occurs that has its center of action at point p'. When this happens the pressure increases in the upper chambers of cylinders 100 and 101. Correspondingly, the pressure in the lower chambers of cylinders 102 and 103 is caused to increase because of the interconnects through the integrating cylinders. This tends to counterbalance the eccentric load. Further, there is no counterforce applied to the main forging force since the forces generated in the cylinders 100-103 are exactly equal and opposite.

We claim:

1. In a press of the type including a movable platen and a fixed platen which cooperate with one another along a line of action to fonn material therebetween, counterbalancing means for counterbalancing eccentric reaction loads on said platens, said counterbalancing means including at least one pair of double acting hydraulic cylinders positioned on opposite sides of said line of action, said cylinders including a cylinder structure and a rod structure, one of said structures being connected with said movable platen, each of said cylinders having corresponding first and second chambers, hydraulic integrating means interconnecting said first chambers with one another and interconnecting said second chambers with one another, said hydraulic integrating means including control means responsive to an increase in pressure in said first chamber of one of said cylinders to decrease the pressure in the first chamber of the other of said cylinders and being responsive to an increase in pressure in said second chamber of one of said cylinders to decrease the pressure in the second chamber of the other of said cylinders.

2. The device of claim 1, and further including locking cylinder means associated with each of said double-acting hydraulic cylinders. 

1. In a press of the type including a movable platen and a fixed platen which cooperate with one another along a line of action to form material therebetween, counterbalancing means for counterbalancing eccentric reaction loads on said platens, said counterbalancing means including at least one pair of double acting hydraulic cylinders positioned on opposite sides of said line of action, said cylinders including a cylinder structure and a rod structure, one of said structures being connected with said movable platen, each of said cylinders having corresponding first and second chambers, hydraulic integrating means interconnecting said first chambers with one another and interconnecting said second chambers with one another, said hydraulic integrating means including control means responsive to an increase in pressure in said first chamber of one of said cylinders to decrease the pressure in the first chamber of the other of said cylinders and being responsive to an increase in pressure in said second chamber of one of said cylinders to decrease the pressure in the second chamber of the other of said cylinders.
 2. The device of claim 1, and further including locking cylinder means associated with each of said double-acting Hydraulic cylinders. 